1. Field of the Invention
The present invention relates to a feed device and to an image forming apparatus such as a photocopier, a printer, and a facsimile machine including the feed device. More particularly, the present invention relates to replacement of a feed device, or feed rollers.
2. Description of Related Art
A related art image forming apparatus forming an image on a recording medium includes a feed device separating plural recording media stacked on a medium tray sheet by sheet and feeding each of the recording media toward an image forming unit. A feed roller is generally used for such separation of the recording media by the feed device. The feed roller is rotated by prescribed power supplied from a power source and contacts an uppermost recording medium, thereby separating the plural recording media sheet by sheet. A surface of the feed roller is made of, for example, a rubber material having a high friction coefficient such that no slide occurs between the surface of the feed roller and the recording medium by friction force. In a case where such a feed roller is used to feed the recoding medium, the feed roller is not only abraded but also conveyability thereof is deteriorated over time due to adhesion and accumulation of dust of the recording media and conveyance of the recording media using the friction force. Consequently, in a case where the feed roller is deteriorated over time, the feed roller needs to be replaced. In addition, for example, a feed device of recent years is expected to have a long life span from an environmental standpoint, and the replacement of only an abraded feed roller having the deteriorated conveyability enhances a reduction of the environmental load.
The replacement of a consumable item such as the feed roller is generally performed by a repair service person. A user of the related art image forming apparatus, however, is expected to replace the consumable item to meet a recent demand of labor saving, cost reduction, and promptness, for example. Here, the replacement of the consumable item needs to be easy so that a user having a lack of machine knowledge can perform the replacement. The replacement of the consumable item of the related art image forming apparatus, however, consumes the time due to complexity of replacement work or due to necessity of disassembling elements although the consumable item is easily detached from a unit body. In addition, in a case where the unit body as a whole is replaced, a cost is increased.
For example, each of Japanese Un-examined Patent Application Publications No. 2000-128368 (Patent Document 1) and No. 2001-26325 (Patent Document 1) discloses a feed device having a feed roller capable of being replaced easily.
The feed device disclosed in the patent document 1 includes bearings disposed both ends thereof, and each of the bearings includes an opening in a circumference direction thereof such that the feed roller is detachable with respect to a bracket having a fastener by a snap-fit method. Herein, the snap-fit method is used in a case where a component is attached to a resin member. For example, the fastener sized smaller than the component is disposed on the side of the resin member, and the component is attached to the resin member by the fastener serving as a spring upon insertion of the component in the fastener. The feed roller attached by such a method engages with a shaft connected to a power source disposed parallel thereto, thereby being rotatable.
Since the power is supplied to the feed roller through the shaft in the feed device disclosed in the document 1, the shaft needs a gear on the side of at another shaft, causing complexity of the feed device. Moreover, since the feed device is detachably disposed by the snap-fit method, the bearing is applied with an excess load.
In the feed device disclosed in the patent document 2, each phase of a drive connection unit needs to be congruent one another in a case of attaching the feed roller, causing difficulty of replacing the feed roller. The patent document 2 also discloses a method for controlling the feed roller with respect to each rotation. However, in a case where the feed device halts in a state that the phases of the connection unit are not congruent, the feed roller cannot be replaced. Such control of the feed roller with respect to each rotation allows a conveyance distance for one feeding operation to be constant, causing an increase in difficulty of feeding the recording media having different sizes or a slippery recording media having a low friction coefficient. Consequently, design flexibility of the feed device becomes limited.
The present invention provides a feed device having a feed roller capable of being replaced easily with a simple structure and reducing occurrences of applying an excess load to a bearing. Moreover, the present invention provides an image forming apparatus having such a feed device.